Alteration of T Cell Subtypes in Beta-Thalassaemia Major: Impact of Ferritin Level

Pathomechanisms of Immunological Disturbances in β-Thalassemia

Thalassemia, a chronic disease with chronic anemia, is caused by mutations in the β-globin gene, leading to reduced levels or complete deficiency of β-globin chain synthesis. Patients with β-thalassemia display variable clinical severity which ranges from asymptomatic features to severe transfusion-dependent anemia and complications in multiple organs. They not only are at increased risk of blood-borne infections resulting from multiple transfusions, but they also show enhanced susceptibility to infections as a consequence of coexistent immune deficiency. Enhanced susceptibility to infections in β-thalassemia patients is associated with the interplay of several complex biological processes. β-thalassemia-related abnormalities of the innate immune system include decreased levels of complement, properdin, and lysozyme, reduced absorption and phagocytic ability of polymorphonuclear neutrophils, disturbed chemotaxis, and altered intracellular metabolism processes. According to available literature data, immunological abnormalities observed in patients with thalassemia can be caused by both the disease itself as well as therapies. The most important factors promoting such alterations involve iron overload, phenotypical and functional abnormalities of immune system cells resulting from chronic inflammation oxidative stress, multiple blood transfusion, iron chelation therapy, and splenectomy. Unravelling the mechanisms underlying immune deficiency in β-thalassemia patients may enable the designing of appropriate therapies for this group of patients.

Low IL-2 Expressing T Cells in Thalassemia Major Patients: Is It Immune Aging

Several studies have demonstrated T cell alteration and some features of immunosenescence in thalassemia major. Repeated alloimmunization converts naïve T-cells to memory cells and iron overload causes oxidative stress accelerating immune aging. To determine whether the alteration of T-cell cytokine is matched with early immune aging, the quantity of cytokine expressing T cells and their correlation to some immune aging markers were investigated. The proportion of IL2- and IFNγ expressing CD4+ and CD8+ T-cells was measured in 27 hepatitis B, C and HIV negative B-thalassemia patients and a control group aged 10-30 years, following stimulation for 6 h with streptococcus enterotoxin B and intracellular cytokine staining. This proportion then were analyzed versus the percentage of the T-cells expressing each phenotyping marker, CD27, CD28, CD57 and CCR7. CD4+ and CD8+ positive T cells expressing IL-2 were significantly lower in β-thalassemia major compared to matched controls, but not T cells expressing IFNγ. No significant difference was observed between splenectomized and non-splenectomized patients in cytokine expressing T cells. A negative correlation was noted between the percentage of T cells expressing IFNγ and T-cells expressing CD-27, but not other markers. Lower T cells expressing IL-2 may reveal the decline of naïve and central memory T cells and is likely to be a feature of early immune aging. Decreased antigenic stimulation and iron overload may help to prevent this phenomenon.